This invention relates to photovoltaic conversion, and, more particularly, to solar cells having improved photovoltaic conversion efficiency.
Solar energy offers the potential for providing virtually unlimited energy for use by man, if the solar energy can be made available in a useful form. Much attention has been directed to the problem of using the sun's energy to obtain electricity, which can then be utilized through existing networks. One of the several approaches to generating electricity from solar radiation is the direct generation of electricity by photovoltaic converters.
At the heart of a photovoltaic converter is a photovoltaic cell, also sometimes termed a solar cell. The photovoltaic cell includes a semiconductor material having at least one P-N junction therein. Light falling upon the junction produces mobile electrical carriers in the form of electron-hole pairs, which can then be directed to an external electrical circuit. The operation of photovoltaic cells is described more fully in U.S. Pat. No. 4,234,352, whose disclosure is herein incorporated by reference.
The economics of using photovoltaic cells for many common applications is determined by the efficiency of the cell in converting sunlight to electrical energy. If the efficiency is low, large numbers of cells are required to provide the required electrical current, and the cost of the large number of cells may dictate the use of another energy source. By way of example, the presently most attractive material for construction of photovoltaic cells is silicon. The theoretical maximum conversion efficiency for silicon cells is about 36 percent using sunlight, and cells approaching 30 percent efficiency have been constructed. However, reaching this level of efficiency has required increasingly complex and costly designs for the photovoltaic cells themselves.
There exists a continuing need for modifications to photovoltaic converter design that increase the conversion efficiency of the system toward its maximum possible value. The present invention fulfills this need, and further provides related advantages.